The present invention relates to a wood treating method and apparatus for treating woods which are slender or curved, for example, soft woods, such as Japanese cedars, Japanese larches, poplars and albizias, or woods from thinning, such as Japanese cedars and Japanese cypresses removed during growth, for strengthening, straightening and free-form shaping, to achieve high added values and effective utilization of woods.
Soft woods, such as Japanese cedars, though utilized as building materials, are limited in use because of their low strength. Further, woods left unused, such as Japanese larches, poplars and albizias, and woods from thinning, such as Japanese cedars and Japanese cypresses removed during growth, are small-diameter woods and, moreover, curved and excessively soft; thus, they are either left unused or discarded.
Accordingly, it has been usual practice to inject a resin, such as phenol resin, into woods, to strengthen the latter by the curing of the resin. However, since a large amount of resin has to be injected into wood, the resin cost is high and so is the treating cost. Further, a special injection device, a period of time (about one day) and substantial labor are required in order to inject resin uniformly into wood. At present, injection of resin into wood is very difficult. Further, since resin is injected into wood for strengthening purposes, the water absorption property which is characteristic of wood is lost, resulting in the wood assuming the plastic property, while losing its performance, functions and properties. Furthermore, if such treated wood is discarded as a waste material, a problem of pollution is raised by the resin during incineration (smoke from harmful materials, influences of high temperature on the incinerator, etc.).
Studies have been made for strengthening wood without using resin; for example, a study of compacting process based on heat treatment using microwaves has been made. However, no effective method has been found as yet for fixing a deformation produced by compaction. That is, absorbing an amount of water corresponding to compaction, the wood is restored to its original shape. Further, microwaves are limited in penetration depth, so that it is difficult to treat thick wood, and the cost is high.